Geologic implications of new zircon U‐Pb ages from the White Mountain Peak Metavolcanic Complex, eastern California

Abstract

[1] The NNW-trending White-Inyo Range includes intrusive and volcanic rocks on the eastern flank of the Sierran volcano-plutonic arc. The NE-striking, steeply SE-dipping Barcroft reverse fault separates folded, metamorphosed Mesozoic White Mountain Peak mafic and felsic volcanic flows, volcanogenic sedimentary rocks, and minor hypabyssal plugs on the north from folded, well-bedded Neoproterozoic-Cambrian marble and siliciclastic strata on the south. The 163 ± 2 Ma Barcroft Granodiorite rose along this fault, and thermally recrystallized its wall rocks. However, new SHRIMP-RG ages of magmatic zircons from three White Mountain Peak volcanogenic metasedimentary rocks and a metafelsite document stages of effusion at $115-120 Ma as well as at $155-170 Ma. The U-Pb data confirm the interpretation by Hanson et al. (1987) that part of the metasedimentary-metavolcanic pile was laid down after Late Jurassic intrusion of the Barcroft pluton. The Lower Cretaceous, largely volcanogenic metasedimentary section lies beneath a low-angle thrust fault, the upper plate of which includes interlayered Late Jurassic mafic and felsic metavolcanic rocks and the roughly coeval Barcroft pluton. Late Jurassic and Early Cretaceous volcanism in this sector of the Californian continental margin, combined with earlier petrologic, structural, and geochronologic studies, indicates that there was no gap in igneous activity at this latitude of the North American continental margin.

Accretion of the Franciscan Complex attending Jurassic-Cretaceous geotectonic development of northern and central California

“…150-135 Ma (Crowder and Sheridan, 1972;Dunne et al, 1978Dunne et al, , 1998Hanson et al, 1987). Employing secondary ion mass spectrometry (SIMS) techniques, Scherer et al (2008) demonstrated that in the White Mountain Peak area, volcanism occurred during the interval ca. 155-110 Ma.…”

“…170 Ma, and that the so-called mag-matic gap at ca. 140-125 Ma in the arc (Stern et al, 1981;Chen and Moore, 1982;Hacker et al, 1995;Wooden et al, 1999) might have been due to an increased ratio of volcanism to plutonism-combined with subsequent preferen tial erosion of the extrusive units-rather than to a period of oblique-convergence-induced igneous quiescence (Glazner, 1991;Bateman, 1992;Scherer et al, 2008). Calc-alkaline volcanism thus seems to have characterized the active continental margin arc over the entire interval from ca.…”